Do While Java 用法

Java Programming

Do-while loops are an essential feature in the Java programming language that allows me to execute a block of code repeatedly based on a condition. In this article, I will dive deep into the usage of do-while loops in Java and share my personal insights and experiences.

What is a do-while loop?

A do-while loop is a control flow statement that executes a block of code at least once, and then repeats the execution as long as a specified condition is true. The structure of a do-while loop in Java looks like this:

do {
// code to be executed
} while (condition);

The key difference between a do-while loop and a regular while loop is that the code block in a do-while loop is executed before checking the condition. This means that the code inside the do block will always run at least once.

When to use a do-while loop?

Do-while loops are particularly useful when we want to execute a certain block of code at least once, even if the condition is initially false. For example, imagine a scenario where I want to prompt the user for input until they enter a valid value. In this case, a do-while loop would be a perfect fit:

Scanner scanner = new Scanner(;
int userInput;

do {
System.out.print("Please enter a positive number: ");
userInput = scanner.nextInt();
} while (userInput <= 0);

In the above example, regardless of the initial value of userInput, the prompt will always be displayed at least once. If the user enters a positive number, the loop will break. Otherwise, the prompt will be displayed again until a valid input is provided.

Personal Reflection

Do-while loops have been incredibly useful in my own programming journey. They have allowed me to write more flexible and interactive programs that can handle various scenarios. I remember a project where I had to simulate a game of dice rolling, and I used a do-while loop to keep rolling the dice until a certain condition was met. It made the implementation much cleaner and more efficient.

One thing to keep in mind when using do-while loops is to ensure that the condition will eventually become false. Otherwise, you might end up with an infinite loop, which can crash your program or cause unexpected behavior. It's always a good practice to test your code thoroughly and consider all possible scenarios.


In conclusion, do-while loops are a powerful construct in Java that allow us to execute a block of code repeatedly based on a condition. They are especially useful when we want to ensure that the code block is executed at least once, regardless of the initial condition. I have personally found do-while loops to be invaluable in my programming journey, enabling me to create more dynamic and interactive applications. As with any programming concept, it's important to practice and test your code to ensure correct usage. Happy coding!